Flow stator for turbomachine with integrated and attached platforms

ABSTRACT

A stator ring of a flow path, preferably secondary, of a turbomachine, the ring including an inner platform and an outer platform, a plurality of stators extending radially between the two platforms, in which at least one of the two platforms includes a plurality of integrated platforms, each one of the integrated platforms being integral with one of the stators, and the integrated platforms are all of the same shape as one another, and a plurality of attached platforms, each one of the attached platforms being in the form of a part that is assembled and arranged between two integrated platforms, and the attached platforms are also all of the same shape as one another.

GENERAL TECHNICAL FIELD

The invention relates to a turbomachine air flow stator ring comprising stator vanes and/or a plurality of structural arms. The invention applies in particular to double flow turbomachines.

PRIOR ART

A double flow turbomachine for aeronautical propulsion is shown in FIG. 1 a. It comprises a fan 10 delivering a flow of air of which a central portion, called the primary flow FP, is injected into a primary flow path comprising a compressor 12 which supplies a turbine 14 driving the fan.

The peripheral portion of the air flow, called the secondary flow FS, which circulates in a secondary flow path, is for its part ejected into the atmosphere to supply the major portion of the thrust of the turbomachine 1, after having passed through a stator 40 ring 20 disposed downflow path of the fan. The stators have aerodynamic profiles and extend in a radial direction (FIG. 1b ).

This annulus, called a stator ring 20, (also known by the acronym OGV for “outlet guide vane”), allows the secondary air to be straightened when leaving the fan, while limiting head losses. This stator ring 20 is preferably situated at an intermediate casing.

Depending on their azimuthal position (3H, 6H, 9H, etc.), the stators 40 generally have different types of aerodynamic profiles P1, P2, P3 . . . , meaning that they do not all have the same camber. In certain turbomachines, as many as seven profiles can be counted. The different cambers can serve to compensate different passage cross sections between stators 40, due the fact of utility passages, as explained in the following paragraph.

In the same FIG. 1 a, which illustrates an embodiment of the turbomachine, is shown a structural arm 30, which connects the external collar 16 of the intermediate casing to the hub 17 of the intermediate casing, thus contributing to supporting and to retaining in position the engine shaft(s) 18 and insuring the structural strength of the assembly. The structural arm also has as its function to allow the transmission of movement or of fluids between the turbomachine and the rest of the aircraft on which it is mounted. To accomplish this, the structural arm is hollow, and allows the accommodation of channels, transmission shafts, etc.

The structural arm can possibly be integrated into the stator ring 20; it thus also provides the function of a stator 40.

In other embodiments, the stator ring 20 does not comprise any structural arm and is purely aerodynamic.

However, the stators can perform the load bearing role, distributed over the entire annulus.

The stator ring 20 must also ensure the aerodynamic continuity of the secondary flow path; to this end, it must reconstitute the secondary flow path between each stator 40 of the ring 20.

Thus, the ring 20 comprises an internal platform 50 and an external platform, between which that stators 40 extend radially.

Turbomachines are known for which the platforms are attached (see FIG. 1c ), meaning that between two adjacent stators 40 is positioned a plate, the structure of which is molded to the shape of the hub. Two adjacent stators 40 possibly having different profiles, it is necessary to have a number of plates of different shapes to be able to create a sealed platform with the stators 40, which is expensive, complicated and risky as regards installation error. In addition, considerable clearance is observed between the plates and the stators (from 3 to 4 mm), which are filled in by silicone seals. However, the silicon seal is difficult to remove and leaves residues.

As a result, manufacturing costs, the risks of error during assembly and the disassembly time for maintenance are increased.

Also known are turbomachines for which the platforms are integrated, meaning that the platforms are integral with the stators. Sealing is easier to accomplish but the stator ring becomes more delicate to disassemble. Reference can be made to document FR2998610 for a solution facilitating the installation of the seal by means of a recess.

There exists a need to simplify both assembly and maintenance, without however causing additional complexity in manufacturing.

PRESENTATION OF THE INVENTION

The invention relates to a stator ring of a preferably secondary flow path of a turbomachine, said stator being configured to be disposed at the exterior of a hub and radially in the interior of an external collar, said stator comprising:

-   -   an internal platform, which forms the flow path at the hub,     -   an external platform, which forms the flow path at the external         collar,     -   a plurality of stators extending radially between the two         platforms, characterized in that:

at least one of the two platforms comprises:

-   -   a plurality of integrated platforms, each of the integrated         platforms being integral with one of the stators, and     -   a plurality of attached platforms, each of the attached         platforms being in the form of a part assembled and disposed         between two integrated platforms.

The assembly and disassembly of the stator is thereby simplified.

In one embodiment, the two platforms each comprise:

-   -   a plurality of integrated platforms, each of the integrated         platforms being integral with one of the stators, and     -   a plurality of attached platforms, each of the attached         platforms being in the form of a part assembled and disposed         between two integrated platforms.

In one preferred embodiment, the integrated platforms of the internal or external platform have the same shape, so that the attached platforms also have the same shape.

By shape is meant the geometry of the contour.

By having identical geometries for the integrated platforms, the attached platforms can be identical, hence a reduction in the risks of error during assembly and a reduction in the cost of manufacturing.

Finally, the stator can comprise the following features taken along or in combination:

-   -   the shape of the integrated platforms is determined by the         stator comprising the most curved camber line,     -   the shape of the integrated platforms is determined by the         stator having maximum bulk,     -   the maximum bulk is determined by the superposition of the         profiles of the stator comprising the most curved camber line         and of the stator comprising the least curved camber line,     -   the integrated and attached platforms are superposed to         facilitate sealing,     -   the integrated platforms comprise at least one step configured         to receive by superposition the attached platforms,     -   the stators comprise at least one attachment root allowing the         attachment of the stator to the external collar or to the hub,         said root being situated in the continuation of the stator,         beyond the integrated platform, so that the root is situated         outside the flow path,     -   the stators and the integrated and attached platforms are made         of composite material,     -   at least one stator comprises a structural arm,     -   the flow path is a secondary turbomachine flow path.

Finally, the invention proposes a double flow turbomachine, comprising a hub, an external collar and a secondary flow stator as described previously. The external collar and the hub delimit a secondary flow path in the interior of which said secondary flow is configured to pass.

In one embodiment, the double flow turbomachine comprises, in its stator ring, at least one stator which is a structural arm.

In one embodiment, the double flow turbomachine comprises, in its stator ring, at least one stator which is a structural arm with utilities, at least one stator which is a structural arm without utilities, and at least one stator which is a non-structural vane.

PRESENTATION OF THE FIGURES

Other characteristics, aims and advantages of the invention will be revealed by the description that follows, which is purely illustrative and not limiting, and which must be read with reference to the appended drawings, in which:

FIG. 1a , already described, shows schematically a double flow turbomachine,

FIG. 1 b, already described, shows a stator,

FIG. 1c shows a platform of the prior art,

FIGS. 2a, 2b, 2c shows an embodiment of a stator according to the invention,

FIG. 3 shows in internal platform according to an embodiment of the invention,

FIGS. 4 and 5 illustrate the design constraints of an embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIGS. 1a and 1 b, a stator ring 20 of a secondary flow vane is shown (labeled FS, like the secondary flow) of a turbomachine 1.

As indicated in the introduction, the stator ring 20 is disposed radially at the exterior of the hub 17 and radially in the interior of the external collar 16. The stator ring serves to straighten the secondary flow originating in the fan 10.

Nevertheless, the stator ring as described in the present application is not limited to this secondary flow path. In particular, it could be implemented in the primary flow path.

The stator ring 20 comprises a plurality of stators 40 distributed regularly around an annulus (not shown) centered on an axis X-X of the turbomachine, corresponding to the axis of the engine shaft (FIG. 1a ). The stators 40 therefore extend radially around the axis X-X′.

Referring to FIGS. 2a, 2b, 2c , the stator 40 conventionally comprises a leading edge 41 a, a trailing edge 41 b, and a camber line 41 c extending from the leading edge 41 a to the trailing edge 41 b, the camber line being the line halfway between the pressure surface and the suction surface of the stator, the pressure surface being the hollow concave surface of the stator, the suction surface being the convex surface of the stator.

The stator comprises an extension direction and two ends 42, 44: an internal end 42, positioned at the hub 17 and an external end 44, positioned at the external collar 16.

The stators 40 are preferably made of composite material. Stators made of metal can also be considered.

The turbomachine can also comprise a structural arm 30 integrated in a stator 40. The structural arm 30 is of the “integrated stator vane” type, meaning that it comprises an end portion having the profile of a stator vane. For the rest of the description, this structural arm 30 will be considered to be a stator 40.

The structural arm 30 comprises a radial cavity for the passage of utilities in particular, but there can exist structural arms 30 without passage of utilities, which can for example be called “elementary” arms. In this case, the structural arm participates in the transmission of loads between the collar and the hub, without however being hollow to receive utilities and/or a power transmission shaft. These elementary structural arms have an aerodynamic profile and a bulk which are close to the profile and the bulk of the non-structural stator vanes, the role of which is solely aerodynamic.

The structural arm 30 is advantageously of the auxiliary type, meaning that its main function is that of transmitting the power of the turbomachine to the rest of the airplane.

It should be noted that hybrid designs are possible, in which all the stators contribute to load bearing, without however being used to pass utilities or power.

In one embodiment, the stator ring 20 comprises at least one stator 40 which is a structural arm 30 with utilities, at least one stator 40 which is a structural arm 30 without utilities, and at least one stator 40 called purely aerodynamic, i.e. not a structural arm (called a non-structural vane), and specifically not allowing the passage of utilities.

Other configurations are possible, particularly without passage of utilities (at least one structural arm and a purely aerodynamic stator).

The stator ring 20 also comprises an internal platform 52, 56 which ensures the aerodynamic continuity of the secondary flow path at the hub 17 and comprises an external platform 54, which ensures the aerodynamic continuity of the secondary flow path at the external collar 16.

The stators 40 therefore extend between the two platforms, internal and external.

The internal, respectively external platform, is designed to be engaged in an accommodation (not shown) provided in the external surface of the hub 17, respectively the internal surface of the external collar 16.

Hereafter, the description will be given for the internal platform. However, unless the contrary is stated, the same features can apply in a similar manner to the external platform.

As shown in FIG. 3, the internal platform 52, 56 comprises two types of elements: integrated platforms 52 and attached platforms 56.

Each stator 40 comprises at its internal end 42 an integrated platform 52 in a single piece. The stator 40 and the integrated platform 52 form the same, single piece, made during the same steps (for example by molding in composite material).

The dimensions of these integrated platforms 52 are such that they do not touch one another (along a periphery of the hub) when they are installed.

In order to reconstruct the internal platform of the secondary flow path, the other type of element is formed by the attached platforms 56, i.e. independent parts which it is desired to assemble to the integrated platforms 52. Each attached platform 56 is situated on the external periphery of the hub 17, between two integrated platforms 52.

The stator ring thus comprises a plurality of stators 40, a plurality of integrated platforms 52 and a plurality of attached platforms 56. There are as many attached platforms 56 as stators 40 (leaving out design exceptions).

Such a configuration allows simplifying access to the hub 16 and allows simpler sealing solutions.

The integrated platforms 52 appear in the form of a doubly curved plate, of which one curvature is centered on the axis X-X′, to follow the shape of the hub, and of which another curvature has the aim of following substantially the camber line of the stator 40. It is possible to define a length along the axis X-X′, and a width along an axis orthogonal and tangential to the platform.

The stator 40 extends vertically from the integrated platform 52 and the substantially centered there. This signifies that a portion of the integrated platform is located on either side of the stator, particularly in the direction of other stators.

The attached platforms 56 appear in the form of a plate having the same types of curvatures.

It has been previously stated that there existed several types of profiles for the stators. These different types of profiles ensure that the stators 40 are not all identical and that consequently, the integrated platforms 52 can also not all be identical. It would then be necessary that the attached platforms 56 all be different to adapt to each pair of integrated platforms 52 situated on either side.

In order to avoid this pitfall, the integrated platforms 52 have the same shape. Same shape means that the shape, that is the geometry of the contour which is in contact with the hub 17, is the same. In other words, the radial projection onto the hub 17 is the same. In other words, the bulk at the internal platform is the same for each integrated platform 52.

It will be understood without difficulty that the expression “same shape” refers to the internal platform and that another “same shape” is defined for the external platform.

This homogenization allows the use of a standard attached platform 56 shape, i.e. that all the attached platforms are identical (excepting details such as openings for cables and others) and interchangeable, and can be designed with the same mold.

The risks of improper assembly are then substantially reduced and the manufacture of the internal platform is simplified.

In fact, the stators 40 and the platforms are generally made of composite material, i.e. they are produced by molding resin with a reinforcement matrix. Details on the production in composite material of stators are found in document WO2014076408.

As the stators 40 have different profiles, they already require as many adapted molds. Consequently, it is sufficient to adapt each mold, but their number remains the same. A single mold is sufficient for producing all the attached platforms 56.

In order for the integrated platforms 52 to have the same shape (or the same geometry), it is necessary to take into account the shape of all the stators 40 and their camber line 41 c. In fact, it is well understood in the light of FIG. 4 (different stator profiles) and 5 (shape of a platform capable of all stator profiles 40) that the most curved camber line and the least curved camber line determine the shape of the integrated platform 52, because they determine the maximum bulk.

Based on this geometry, it is possible to then define the geometry of the attached platform 56, which will be identical for all attached platforms 56 of the periphery of the hub 17.

Thus, by superposing the most cambered profile and the least cambered profile, the shape of the integrated platform common to all the other intermediate profiles is known.

A similar method is carried out for the attached platforms of the external collar.

In the case of a stator comprising a structural arm, it is generally this stator which will determined the shape, because it is most constraining aerodynamically and has the maximum bulk.

The internal platform is made using integrated 52 and attached 56 platforms. There are consequently two seals to be provided for each attached platform 56. Nevertheless, due to the standardization of the shapes of the platforms, the clearances involved are smaller and sealing is thereby improved.

In order to favor the latter, the integrated 52 and attached 56 platforms are assembled by partial covering, i.e. each part covers or is covered slightly.

In a first embodiment of partial covering, the integrated platforms 52 comprise steps 58, i.e. a double folding of an edge of the platforms to arrive at two parallel planes, offset by a distance of substantially the same order of magnitude as the thickness of the edge. The step of the stator 40 extends over the lengths of the integrated platform 52. The attached platforms 56 are disposed on the step and engage with the latter, which makes it possible to ensure aerodynamic continuity (the internal platform is flat) and a good seal.

In a second similar embodiment it is the attached platforms which comprise the steps.

In a third similar embodiment, it is an edge of the attached platforms 56 and an edge of the integrated platforms 54 which include a step 58. In this case, the step is covered by the unstopped edge of the other element.

The first mode will be favored for reasons of assembly: the stators 40 are placed first, then the attached platforms 56.

In one embodiment, only one of the two platforms (internal or external) comprises integrated and attached platforms, with possibly the previously described features.

In a preferred embodiment, the preceding detailed description applies to the two platforms (internal and external). It will be understood that, due to the spreading induced by the radial arrangement of the stators, the width of the attached platforms of the external platform is greater than that of the attached platforms 56 of the internal platform. On the other hand, the integrated platforms 54 of the external platform can have substantially the same dimensions as the integrated platforms 52 of the internal platform.

In addition, due to the shape of the flow path, for example of the secondary flow path, the concavity of the platforms between the internal and the external platform is reversed.

In the case where integrated platforms of the same shape are used on the internal platform and on the external platform, two different shapes of attached platforms are therefore obtained.

In order to allow the attachment to the hub 17 or to the external collar 16, each stator 40 comprises attachment means 60 in the form of an internal root 62 (for attachment to the hub 17) and of an external root 64 (for attachment to the external collar).

The root 62, 64 are an integral part of the stator and are made in a single piece.

They can typically comprise a plurality of transverse opening in the extension direction of the stator 40.

The attachment means must not interfere with the flow of fluid in the secondary flow path and for this reason they are disposed outside this flow path. The root 62, respectively 64, are disposed beyond the integrated platforms 52, respectively 54.

Depending on the extension direction of the stator 40, the internal root 62, the integrated platform 52 (internal), the stator 40, the integrated platform 56 (external), the external root 64 are then obtained.

The stator ring can be implemented over the entire turbomachine requiring such a ring, and over the entire aircraft requiring such a turbomachine.

Finally, the invention also relates to a mold (not shown in the figures) for manufacturing the vanes 40 and their respective integrated platform. Two other molds are advantageously provided for manufacturing the attached platforms of the internal and external platform. 

1. A double flow turbomachine comprising a hub, an external collar delimiting with the hub a secondary flow path, and a stator ring of the secondary flow path circulating in said secondary flow path, said ring comprising: an internal platform, which forms the flow path at the hub, an external platform, which forms the flow path at the external collar, a plurality of stators extending radially between the two platforms, wherein: at least one of the two platforms comprises: a plurality of integrated platforms, each of the integrated platforms being integral with one of the stators and the integrated platforms all having the same shape, and a plurality of attached platforms, each of the attached platforms being in the form of a part assembled and disposed between two integrated platforms, and the attached platforms also having the same shape.
 2. The double flow turbomachine according to claim 1, wherein the two platforms each comprise: a plurality of integrated platforms, each of the integrated platforms being integral with one of the stators and the integrated platforms all having the same shape, and a plurality of attached platforms, each of the attached platforms being in the form of a part assembled and disposed between two integrated platforms, and the attached platforms also having the same shape.
 3. The double flow turbomachine according to claim 1, wherein the shape of the integrated platforms is determined by the stators having maximum bulk.
 4. The double flow turbomachine according to claim 3, wherein the maximum bulk is determined by the superposition of the profiles of the stator comprising the most curved camber line and of the stator comprising the least curved camber line.
 5. The double flow turbomachine according to claim 1, wherein the integrated and attached platforms are superposed to facilitate sealing.
 6. The double flow turbomachine according to claim 1, wherein the integrated platforms comprise at least one step configured to receive by superposition the attached platforms.
 7. The double flow turbomachine according to claim 1, wherein the stators comprise at least one attachment root allowing the attachment of the stator to the external collar or to the hub, said root being situated in the continuation of the stator, beyond the integrated platform, so that the root is situated outside of the secondary flow path.
 8. The double flow turbomachine according to claim 1, wherein the stators and the integrated and attached platforms are made of composite material.
 9. The double flow turbomachine according to claim 1, wherein at least one stator is a structural arm.
 10. The double flow turbomachine according to claim 1, wherein at least one stator is a structural arm with utilities, at least one stator is a structural arm without utilities, and at least one stator is a non-structural vane. 